CHAPTER 8 Compounds and Molecules 8.1 Ionic Compounds

2 In early chapters we discussed physical and chemical properties

3 8.1 Ionic Compounds In early chapters we discussed physical and chemical properties In later chapters we discussed atom structures and chemical bonding

4 8.1 Ionic Compounds Physical and chemical properties Atom structures and chemical bonding

5 8.1 Ionic Compounds Ionic compounds (like table salt, NaCl) First we address ionic compounds Physical and chemical properties Atom structures and chemical bonding

6 8.1 Ionic Compounds Molecular compounds (like DNA) Then we will address molecular compounds Physical and chemical properties Atom structures and chemical bonding

7 8.1 Ionic Compounds Each chloride ion is attracted to all nearby sodium ions Each sodium ion is attracted to all nearby chloride ions Structure of NaCl We have seen that in an ionic salt each atom interacts with all its neighbors.

8 8.1 Ionic Compounds In any ionic crystal, the ratio of positive ions to negative ions must allow for all of the positive charge to cancel out all of the negative charge. Lead(II) sulfide (PbS) Aluminum oxide (Al 2 O 3 ) Copper(II) sulfate (CuSO 4 ) Pb 2+ and S 2– (+2) and (–2) 2Al 3+ and 3O 2– (+6) and (–6) Cu 2+ and SO 4 2– (+2) and (–2)

9 8.1 Ionic Compounds The ionic structure leads to the following physical properties: Ionic substances are solid at room temperature To be in a liquid state, there must be enough energy for each atom to break free from the attractive forces from its neighbors. Properties

Ionic Compounds The ionic structure leads to the following physical properties: Ionic substances are solid at room temperature Ionic substances have very high melting points Properties To be in a liquid state, there must be enough energy for each atom to break free from the attractive forces from its neighbors.

Ionic Compounds The interconnected network of bonds holds the entire crystal together The ionic structure leads to the following physical properties: Ionic substances are solid at room temperature Ionic substances have very high melting points Ionic substances are hard Properties

Ionic Compounds Ionic substances are brittle, which means they break The ionic structure leads to the following physical properties: Ionic substances are solid at room temperature Ionic substances have very high melting points Ionic substances are hard but brittle Properties

Ionic Compounds When melted or dissolved, ions are free to move around, making it possible for an ionic solution to conduct electricity Ions dissolved in water move in random directions by colliding with water molecules Overall ion movement toward the electrodes creates an electrical current Properties

Ionic Compounds Polyatomic ions An ion does not have to be a single atom. An ion can be a small molecule with a charge. a polyatomic ion a monatomic ion

Ionic Compounds Polyatomic ions Calcium carbonate, CaCO 3 The calcium ion contributes a +2 charge (Ca 2+ ) The CO 3 molecule needs two extra electrons.

Ionic Compounds Polyatomic ions The two oxygens now have a –1 charge, giving the whole molecule a –2 charge The carbonate ion switches among these three versions.

Ionic Compounds Ammonium sulfate (NH 4 ) 2 SO 4 is made from two polyatomic ions

Ionic Compounds Now we will learn how to: - Write formulas for ionic compounds - Write names for ionic compounds - Name ions with transition metals

Ionic Compounds Balancing positive and negative charge in ionic formula writing Writing formulas

Ionic Compounds Balancing positive and negative charge in ionic formula writing Writing formulas

Ionic Compounds Write the correct formulas for the compounds that will form using the following ion pairs: Mg 2+ and Cl –, Na + and S 2 –, Al 3+ and O 2–. Writing formulas

Ionic Compounds Write the correct formulas for the compounds that will form using the following ion pairs: Mg 2+ and Cl –, Na + and S 2 –, Al 3+ and O 2–. Writing formulas Asked:Ionic formulas for the three different ionic substances Given:The charges on all of the ion pairs Relationships:The positive ions will combine with the negative ions in a ratio so that the positive and negative charges from the ions will be equal.

Ionic Compounds Write the correct formulas for the compounds that will form using the following ion pairs: Mg 2+ and Cl –, Na + and S 2 –, Al 3+ and O 2–. Writing formulas Asked:Ionic formulas for the three different ionic substances Given:The charges on all of the ion pairs Relationships:The positive ions will combine with the negative ions in a ratio so that the positive and negative charges from the ions will be equal. Solve:For each Mg 2+ we need two Cl – (+2 – 1 – 1 = 0) and the formula is MgCl 2.

Ionic Compounds Write the correct formulas for the compounds that will form using the following ion pairs: Mg 2+ and Cl –, Na + and S 2 –, Al 3+ and O 2–. Writing formulas Asked:Ionic formulas for the three different ionic substances Given:The charges on all of the ion pairs Relationships:The positive ions will combine with the negative ions in a ratio so that the positive and negative charges from the ions will be equal. Solve:For each Mg 2+ we need two Cl – (+2 – 1 – 1 = 0) and the formula is MgCl 2. For each S 2– we need two Na + (– = 0) and the formula is Na 2 S.

Ionic Compounds Write the correct formulas for the compounds that will form using the following ion pairs: Mg 2+ and Cl –, Na + and S 2 –, Al 3+ and O 2–. Writing formulas Asked:Ionic formulas for the three different ionic substances Given:The charges on all of the ion pairs Relationships:The positive ions will combine with the negative ions in a ratio so that the positive and negative charges from the ions will be equal. Solve:For each Mg 2+ we need two Cl – (+2 – 1 – 1 = 0) and the formula is MgCl 2. For each S 2– we need two Na + (– = 0) and the formula is Na 2 S. To balance charges between Al 3+ and O 2– we need to multiply Al by 2 and O by 3 [2(+3) + 3(–2) = 0]. The formula is Al 2 O 3.

Ionic Compounds Polyatomic ions represent a single unit with a charge just like single-atom ions Writing formulas

Ionic Compounds Writing formulas with polyatomic ions The chlorate ion (ClO 3 – ) is made by covalently bonding chlorine to three oxygens and adding an extra electron To indicate more than one chlorate, parentheses must be used Writing formulas

Ionic Compounds Writing formulas Write the correct formulas for the compounds that will form using the following ion pairs: Mg 2+ and SO 4 2–, Ca 2+ and PO 4 3–, and NH 4 + and S 2–.

Ionic Compounds Writing formulas Write the correct formulas for the compounds that will form using the following ion pairs: Mg 2+ and SO 4 2–, Ca 2+ and PO 4 3–, and NH 4 + and S 2–. Asked: Ionic formulas for three different ionic substances listed Given:The charges on all of the ion pairs Relationships:The positive ions will combine with the negative ions in a ratio so that the positive and negative charge from the ions will be equal.

Ionic Compounds Writing formulas Write the correct formulas for the compounds that will form using the following ion pairs: Mg 2+ and SO 4 2–, Ca 2+ and PO 4 3–, and NH 4 + and S 2–. Asked: Ionic formulas for three different ionic substances listed Given:The charges on all of the ion pairs Relationships:The positive ions will combine with the negative ions in a ratio so that the positive and negative charge from the ions will be equal. Solve:For each Mg 2+, we need one SO 4 2– (+2 – 2 = 0) and the formula is MgSO 4.

Ionic Compounds Writing formulas Write the correct formulas for the compounds that will form using the following ion pairs: Mg 2+ and SO 4 2–, Ca 2+ and PO 4 3–, and NH 4 + and S 2–. Asked: Ionic formulas for three different ionic substances listed Given:The charges on all of the ion pairs Relationships:The positive ions will combine with the negative ions in a ratio so that the positive and negative charge from the ions will be equal. Solve:For each Mg 2+, we need one SO 4 2– (+2 – 2 = 0) and the formula is MgSO 4. To balance charges between Ca 2+ and PO 4 3–, multiply Ca by 3 and PO 4 by 2: [3(+2) + 2(–3) = 0]. The formula is Ca 3 (PO 4 ) 2.

Ionic Compounds Writing formulas Write the correct formulas for the compounds that will form using the following ion pairs: Mg 2+ and SO 4 2–, Ca 2+ and PO 4 3–, and NH 4 + and S 2–. Asked: Ionic formulas for three different ionic substances listed Given:The charges on all of the ion pairs Relationships:The positive ions will combine with the negative ions in a ratio so that the positive and negative charge from the ions will be equal. Solve:For each Mg 2+, we need one SO 4 2– (+2 – 2 = 0) and the formula is MgSO 4. To balance charges between Ca 2+ and PO 4 3–, multiply Ca by 3 and PO 4 by 2: [3(+2) + 2(–3) = 0]. The formula is Ca 3 (PO 4 ) 2. For each S 2– we need two NH 4 +. The formula is (NH 4 ) 2 S.

Ionic Compounds Writing names With monatomic ions:

Ionic Compounds Writing names Names for polyatomic ions

Ionic Compounds Writing names With polyatomic ions:With monatomic ions:

Ionic Compounds Naming transition metal ions Most transition metals can have different charges Check whether a Roman numeral is necessary for elements in the highlighted parts of the periodic table A Roman numeral indicates the charge on a positive ion

Ionic Compounds Naming transition metal ions Consider PbCl 2 Check the common ions table

Ionic Compounds Naming transition metal ions Consider PbCl 2 Check the common ions table Use the negative ion to determine the charge on lead

Ionic Compounds Naming transition metal ions Consider PbCl 2 Check the common ions table Use the negative ion to determine the charge on lead With only one Pb ion, and a total charge of +2 needed, the Pb ion must be lead(II)

Ionic Compounds Naming transition metal ions Check the common ions table Consider ZnSO 4

Ionic Compounds Naming transition metal ions Check the common ions table Zn only forms a +2 ion No Roman numeral is needed Consider ZnSO 4

Ionic Compounds Write the names for each of the following formulas: CaCl 2, Zn(NO 3 ) 2, Fe 3 (PO 4 ) 2.

Ionic Compounds Write the names for each of the following formulas: CaCl 2, Zn(NO 3 ) 2, Fe 3 (PO 4 ) 2. Asked:Names for the formulas above Given:Three formulas and a common ion table Relationships:The name of each formula is constructed form the name of the ions. If the negative ion is a single atom, modify the name of the element to end in “-ide.” If the positive ion might form multiple charges, make sure to use a Roman numeral in the name.

Ionic Compounds Write the names for each of the following formulas: CaCl 2, Zn(NO 3 ) 2, Fe 3 (PO 4 ) 2. Asked:Names for the formulas above Given:Three formulas and a common ion table Relationships:The name of each formula is constructed form the name of the ions. If the negative ion is a single atom, modify the name of the element to end in “-ide.” If the positive ion might form multiple charges, make sure to use a Roman numeral in the name. Solve:CaCl 2 is calcium chloride.

Ionic Compounds Write the names for each of the following formulas: CaCl 2, Zn(NO 3 ) 2, Fe 3 (PO 4 ) 2. Asked:Names for the formulas above Given:Three formulas and a common ion table Relationships:The name of each formula is constructed form the name of the ions. If the negative ion is a single atom, modify the name of the element to end in “-ide.” If the positive ion might form multiple charges, make sure to use a Roman numeral in the name. Solve:CaCl 2 is calcium chloride. Zn(NO 3 ) 2 is zinc nitrate.

Ionic Compounds Write the names for each of the following formulas: CaCl 2, Zn(NO 3 ) 2, Fe 3 (PO 4 ) 2. Asked:Names for the formulas above Given:Three formulas and a common ion table Relationships:The name of each formula is constructed form the name of the ions. If the negative ion is a single atom, modify the name of the element to end in “-ide.” If the positive ion might form multiple charges, make sure to use a Roman numeral in the name. Solve:CaCl 2 is calcium chloride. Zn(NO 3 ) 2 is zinc nitrate. Fe 3 (PO 4 ) 2 is iron(II) phosphate.

Ionic Compounds The ionic structure leads to the following physical properties: Ionic substances are solid at room temperature Ionic substances have very high melting points Ionic substances are hard but brittle Overall ion movement creates an electrical current

Ionic Compounds We learned how to: Write formulas for ionic compounds Write names for ionic compounds Name ions with transition metals a polyatomic ion